| /* |
| * Copyright (C) 2018 The Android Open Source Project |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| package com.android.permissioncontroller.permission.utils; |
| |
| import android.util.ArraySet; |
| |
| import androidx.annotation.NonNull; |
| import androidx.annotation.Nullable; |
| |
| import java.util.Collection; |
| import java.util.Collections; |
| import java.util.List; |
| |
| /** |
| * Utility methods for dealing with {@link java.util.Collection}s. |
| */ |
| public final class CollectionUtils { |
| |
| private CollectionUtils() {} |
| |
| /** |
| * Check whether a collection is {@code null} or empty. |
| * |
| * @param collection the collection to check |
| * |
| * @return whether the collection is {@code null} or empty |
| */ |
| public static boolean isEmpty(@Nullable Collection<?> collection) { |
| return collection == null || collection.isEmpty(); |
| } |
| |
| /** |
| * Return the first element of a list, or {@code null} if the list is {@code null} or empty. |
| * |
| * @param <T> the class of the elements of the list |
| * @param list the list to get the first element |
| * |
| * @return the first element of the list, or {@code null} if the list is {@code null} or empty |
| */ |
| @Nullable |
| public static <T> T firstOrNull(@Nullable List<T> list) { |
| return !isEmpty(list) ? list.get(0) : null; |
| } |
| |
| /** |
| * Remove all values in the array set that do <b>not</b> exist in the given collection. |
| * |
| * @param <T> the class of the elements to retain and of the {@code ArraySet} |
| * @param arraySet the {@code ArraySet} whose elements are to be removed or retained |
| * @param valuesToRetain the values to be used to determine which elements to retain |
| * |
| * @return {@code true} if any values were removed from the array set, {@code false} otherwise. |
| * |
| * @see ArraySet#retainAll(java.util.Collection) |
| */ |
| @SafeVarargs |
| public static <T> boolean retainAll(ArraySet<T> arraySet, T... valuesToRetain) { |
| boolean removed = false; |
| for (int i = arraySet.size() - 1; i >= 0; i--) { |
| if (!ArrayUtils.contains(valuesToRetain, arraySet.valueAt(i))) { |
| arraySet.removeAt(i); |
| removed = true; |
| } |
| } |
| return removed; |
| } |
| |
| /** |
| * Return a singleton list containing the element, or an empty list if the element is |
| * {@code null}. |
| * |
| * @param <T> the class of the element |
| * @param element the element to be put into the list |
| * |
| * @return a singleton list containing the element, or an empty list if the element is |
| * {@code null}. |
| */ |
| @NonNull |
| public static <T> List<T> singletonOrEmpty(@Nullable T element) { |
| return element != null ? Collections.singletonList(element) : Collections.emptyList(); |
| } |
| } |